In the diagnosis and treatment of breast cancer, it is often necessary to perform a biopsy to remove tissue samples from a suspicious mass. The suspicious mass is typically discovered during a preliminary examination involving visual examination, palpation, X-ray, magnetic resonance imaging (MRI), ultrasound imaging or other detection means.
When a suspicious mass is detected, a sample is taken by biopsy, and then tested to determine whether the mass is malignant or benign. This biopsy procedure can be performed by an open surgical technique, or through the use of a specialized biopsy instrument. To minimize surgical intrusion, a small specialized instrument such as a biopsy needle is inserted in the breast while the position of the needle is monitored using fluoroscopy, ultrasonic imaging, X-rays, MRI or other suitable imaging techniques.
In one biopsy procedure, referred to as stereotactic needle biopsy, the patient lies on a special biopsy table with her breast compressed between the plates of a mammography apparatus and two separate X-rays are taken from two different points of reference. A computer then calculates the exact position of the mass or lesion within the breast. The coordinates of the lesion are then programmed into a mechanical stereotactic apparatus which advances the biopsy needle into the lesion with precision. At least five biopsy samples are usually taken from locations around the lesion and one from the center of the lesion.
Regardless of the method or instrument used to perform the biopsy, subsequent examination of the surgical site may be necessary, either in a follow up examination or for treatment of a cancerous lesion. Treatment often includes a mastectomy, lumpectomy, radiation therapy, or chemotherapy procedure that requires the surgeon or radiologist to direct surgical or radiation treatment to the precise location of the lesion. Because this treatment might extend over days or weeks after the biopsy procedure, and the original features of the tissue may have been removed or altered by the biopsy, it is desirable to insert a site marker into the surgical cavity to serve as a landmark for future identification of the location of the lesion.
Known biopsy site markers have been found to have disadvantages in that the site markers are not visible under all available modalities. Moreover, because of this problem, when cancer is found at a biopsy site that has been previously marked with a site marker, due to the poor visibility of the biopsy site marker under ultrasound or other visualization modalities, the patient must undergo an additional procedure that places an additional device within the biopsy site to enable the surgeon to find the biopsy site in subsequent procedures. One known technique has been to place a breast lesion localization wire at the biopsy site. The localization wire is typically placed at the biopsy site via mammography and/or ultrasound.
Another issue that arises with site markers is migration. When the site markers are typically deployed to the biopsy site, the breast is still under compression. However, when the breast is released from compression, the site marker may migrate within the site or even out of the site through a needle tract created by the biopsy device, thereby preventing a surgeon or radiologist from easily locating the precise location of the lesion or biopsied area.
Accordingly, there is a need for site markers made from biocompatible materials that are visible under various modes of imaging to reduce the number of procedures that patients must undergo in detection and treatment of cancer. There is also a need to limit migration of a site marker when the site marker is placed in a biopsy site.